Ultrawideband Electromagnetic Interference to … Ultrawideband Electromagnetic Interference to Aircraft Radios Results of Limited Functional Testing With United Airlines and Eagles

NASA/TM-2002-211949

Ultrawideband ElectromagneticInterference to Aircraft Radios

Results of Limited Functional Testing With United Airlines

and Eagles Wings Incorporated, in Victorville, California

Jay J. Ely

Langley Research Center, Hampton, Virginia

Timothy W Shaver

United Airlines, Indianapolis, Indiana

Gerald L. Fuller

Eagles Wings Incorporated, Mariposa, California

October 2002

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NASA/TM-2002-211949

Ultrawideband ElectromagneticInterference to Aircraft Radios

Results of Limited Functional Testing With United Airlines

and Eagles Wings Incorporated, in Victorville, California

Jay J. Ely

Langley Research Center, Hampton, Virginia

Timothy W Shaver

United Airlines, Indianapolis, Indiana

Gerald L. Fuller

Eagles Wings Incorporated, Mariposa, California

National Aeronautics and

Space Administration

Langley Research CenterHampton, Virginia 23681-2199

October 2002

The use of trademarks or names of manufacturers in the report is for accurate reporting and does not constitute anofficial endorsement, either expressed or implied, of such products or manufacturers by the National Aeronautics andSpace Administration or the U.S. Army.

Available from:

NASA Center for AeroSpace Information (CASI)7121 Standard Drive

Hanover, MD 21076-1320(301) 621-0390

National Technical Information Service (NTIS)5285 Port Royal RoadSpringfield, VA 22161-2171(703) 605-6000

Abstract

On February 14, 2002, the FCC adopted a FIRST REPORT AND

ORDER, released it on April 22, 2002, and on May 16, 2002 publishedin the Federal Register a Final Rule, permitting marketing and operation

of new products incorporating UWB technology. Wireless productdevelopers are working to rapidly bring this versatile, powe_ul and

expectedly inexpensive technology into numerous consumer wirelessdevices. Past studies addressing the potential for passenger-carriedportable electronic devices (PED_) to inte_ere with aircraft electronic

systems suggest that UWB transmitters may pose a sign_cant threat toaircraft communication and navigation radio receivers. NASA, United

Airlines and Eagles Wings Incorporated have pe_ormed preliminarytesting that clearly shows the potential for handheld UWB transmitters to

cause cockpit failure indications for the air trafJ_c control radio beaconsystem (ATCRBS), blanking of aircraft on the traJfic alert and collision

avoidance system (TCAS) displays, and cause erratic motion and failureof instrument landing system (ILS) localizer and glideslope pointers on

the pilot horizontal situation and attitude director displays. This reportprovides details of the preliminary testing and recommends further

assessment of aircraft systems for susceptibility to UWB electromagneticinte_erence.

1 Background

Ultrawideband (UWB) technology is typically characterized by the radiation and detection of base-band pulse signals, having a duration of less than 1 nanosecond. A periodic sequence of these pulses can

be shown in the frequency domain to appear as narrow-band signals at frequency spacing that is theinverse of the pulse repetition interval. Highly broadband antennas are required to transfer enoughfrequency content through the transmission medium to preserve the required degree of pulse shape

characteristics. The first patent for a UWB-type communication system was issued to Gerald Ross, in1973 [1], however the technology was referred to as baseband at that time. According to Dr. Robert

Fontana, President of Multispectral Solutions Inc., most UWB technology development prior to 1994 wasperformed under classified U. S. government programs [2]. Fontana provides an excellent history of

UWB, with many downloadable references at the Multispectral Solutions website:

In 1994, Thomas McEwan was issued a patent for an "Ultra-Wideband RADAR Motion Sensor" [3],

and was credited with specifying numerous commercial applications for the technology in a PopularScience magazine article entitled "RADAR on a Chip, 101 Uses In Your Life" (June 1995), [4]. Because

UWB technology is inherently a pulse modulated radio transmission scheme, blending of digitalcommunications and radar sensor applications is greatly simplified. Some safety-related UWBapplications address situational awareness needs in automobiles, like backup-warning systems, intelligent

cruise control and collision avoidance. Some security-related UWB applications include sensors that cansee into (and even through) boxes, bags, crates and walls, allowing detection of unauthorized equipment

or intruders. UWB ground penetrating radars have been demonstrated to provide extensive informationabout buried pipes, weapons and facilities for military, geological, archeological and architectural

applications. UWB systems can be implemented with very inexpensive and compact electroniccomponents. Perhaps these characteristics hold the greatest promise for driving a revolution in new

applications for consumer products. Designers and developers of wireless technology are promoting

UWB technology for addressing the needs of high data rates, interoperability and location awareness that

will be required for emerging wireless applications.

2 Status of UWB Regulation

On February 14, 2002, the FCC adopted a FIRST REPORT AND ORDER, released it on April 22,

2002, and on May 16, 2002 published in the Federal Register a Final Rule, permitting marketing and

operation of new products incorporating UWB technology [5]. Years of effort have been invested by the

FCC, the National Telecommunications and Information Administration (NTIA), universities and

industry to develop a technical rationale for setting limits on allowable UWB signal levels. The FCC

Final Rule provides detailed requirements for allowable UWB radiated emission levels. These levels are

based primarily on FCC Part 15.209 spurious radiated emission limits [6]. Additional limitations are

specified depending upon the stated application: imaging systems, vehicular radar systems, indoor UWB

systems, and handheld UWB systems. The technical requirements for handheld UWB systems, as

addressed in FCC Final Rule Part 15.519, are of primary concern when considering UWB technology

applications within PEDs, particularly as a threat to aircraft radios. Handheld UWB system emission

limit levels are specifically provided as effective isotropic radiated power (EIRP) from 960 MHz to above

10.6 GHz. Below 960 MHz, the standard FCC Part 15.209 limits apply. By assuming an isotropic

radiation pattern, the field intensity levels specified in FCC Part 15.209 can be converted to EIRP levels

at frequencies below 960 MHz. The final composite limits, from 100MHz to 10.7GHz are shown in

Figure 1. While UWB operation is stated to be restricted to the 3.1-10.6 GHz frequency band in the FCC

Final Rule, relatively high limits are also allowed for operation below 960MHz.

FCC UWB Limits for Outdoor Handheld Systems

1000 10000

Frequency (MHz)

Figure 1: Composite graph of EIRP allowed by the FCC Final UWB Rule, Part 15.519, dated May 16, 2002.

The FCC FIRST REPORT AND ORDER states that the adopted standards "may be overprotective

and could unnecessarily constrain the development of UWB technology", and reveals the intention to

issue a further rulemaking to "explore more flexible technical standards and to address the operation of

additional types of UWB operations and technology". These statements appear to indicate that a

relaxation of UWB radiated emission limits is planned for the near future. On July 12, 2002, the FCC

issued an additional Order, permitting the continued operation of UWB ground penetrating radars (GPRs)

and wall imaging systems that do not comply with the FCC FIRST REPORT AND ORDER [7]. The July

12 Order applies to GPR's and wall imaging systems that had previously been operating without FCC

licenses, authorized under FCC experimental rules under FCC Part 5 or by waivers. The July 12 Order

cites that several public safety benefits result from the continued operation of existing GPRs and wall

imaging systems currently in use, and that the FCC is not aware of any reports of harmful interference

resulting from the long-term use of these systems in the past.

3 Why is UWB EMI a Concern For Aircraft Radios?

Spurious radiated emission data from typical PED's is available within the RTCA/DO-199 and/DO-

233 publications. (See DO-190 Vol. 2 Section 4.0, and DO-233 Appendix A, [8], [9].) The RTCApublications contain numerous charts, clearly showing that typical PEDs radiate spurious signal

amplitudes that are thousands of time less, at most frequencies, than the FCC 15.209 limits require. Infact, the DO-233 analysis concluded that PEDs meeting FCC 15.209 limits could exceed interference

limits for aircraft VOR and Localizer radios by a factor of over 1000 times, even after their emissions areattenuated by traveling from the passenger cabin to aircraft radio receivers. However, as noted by theDO-233 authors, the probability of a typical device radiating at the FCC limit, on a particular aircraft

radio channel is extremely low. UWB transmitters, on the other hand, emit equal-amplitude, narrow bandsignals at frequency spacing that is the inverse of the pulse repetition interval. When using pulse-position

modulation and different clock frequencies, UWB transmitters emit narrow-band signals simultaneouslyat any frequency, even in safety-critical aircraft bands. There is clearly a very big difference between

typical consumer devices, that radiate spurious signals nearly always far below FCC 15.209 limits, andUWB devices, that may be intentionally designed to radiate at or near FCC 15.209 limits.

The final FCC rule explicitly states that "the operation of UWB devices is not permitted onboard

aircraft, ships, or satellites...". This statement indicates that the FCC has documented EMI concerns forUWB operation on board these vehicles. The FCC rule provides no guidance on how UWB devices can

be restricted from operating in these vehicles, who is responsible for enforcing the restrictions, and whatthe penalties are.

4

4.1

Limited Functional Testing of UWB EMI on United Airlines Airplanes

NASA�Eagles Wings�United Airlines/Eclypse Test Project

To determine the threat power at the connector of a particular aircraft radio receiver, due to thespurious radiated emissions from a PED, losses due to propagation, antenna loss and cable loss occurringbetween the PED and the aircraft radio connector must be known. These losses can be identified as

"interference path loss" (IPL). Since the RTCA/DO-199 & DO-233 studies, significant additional workhas been performed by Eagles Wings Incorporated (EWI), Delta Airlines and NASA to better understand

and quantify IPL. Previous analyses note that there are significant deficiencies in available data to allow

estimation of the probability that a particular passenger location will have an IPL below a particularthreshold [10]. A need was identified to extend the available IPL database on typical commercialtransport aircraft. Such measurements are labor-intensive, and require exclusive access to airplane

interior locations, exterior antenna systems, and avionics bay connections.

EWI submitted a proposal to NASA to work with United Airlines in resolving several technical issues

related to IPL measurement data, including aircraft-to-aircraft repeatability, the type of test antenna, andIPL measurements at all passenger cabin seat locations. The proposal was supplemented with an

evaluation of IPL mitigation techniques (ie. door/window exit seam shielding, and conductive windowfilms), and assessment of aircraft RF cable and antenna health using new-technology instrumentationtools. NASA issued a Purchase Order (L-16099) to work with EWI, United Airlines, and Eclypse on

these goals. United Airlines was able to provide a limited number of flight-ready airplanes at an aviationstorage facility in Victorville, California, including fuel, engineering and mechanic support for this

purpose. Measurements were performed during three one-week visits to the Southern California Aviationfacility, in Victorville, California.

Under the NASA/EWI contract, IPL measurements were performed on 6 B737-200 airplanes at all

windows and door exits, for the VOPULocalizer, VHF-1 comm., Glideslope, TCAS, and GPS radio

antennasystems,andon4 B747-400airplanesat selectedwindowsanddoorexit locations,for theLocalizer,VklF-1comm.,Glideslope,TCAS,GPSandSatcomradioantennasystems.(VORandILSlocalizershareanantennaandRFpathwayon theB737-200.)Duplicatesetsof pathlossdatawereobtainedonmultiple,identicalaircraft,to establishrepeatabilityof themeasurementprocessandtoidentifyanydifferencesrelatedto subtleaircraftconfigurationchanges.(Seeaircraftpicturedin Figure2.) IPLmeasurementswerealsoperformedusinganalternate,electricallysmallbiconicalantennafortheVHFband. Comparisonof biconicalantennadatato standarddipoledatawill provideinsightintomeasurementvariabilityandto identifyadvantagesanddisadvantagesdueto antennatype. Additionalinterferencepathlossmeasurementswereperformedatnumerousseatlocations,toquantifythedegreetowhichinterferencepathlossvariesasthetransmittingsourcemovesawayfromawindow.Theadditionalseatlocationdatamaybeusefulfor assessingtheadditivethreatdueto multipletransmitters.TheNASA/EWIcontractalsoincludedanevaluationof a new-technologyStandingWaveReflectometer,manufacturedby EclypseInc., for measuringvoltagedifferencesonRFtransmissionlinesdueto anappliedsignalof linearly-varyingfrequency.TheStandingWaveRefelectometereasilyconnectsto anaircraftRFsystemwithoutantennaremoval,andprovidesdistinctlydifferentoutputindicationsduetoantennaoraircraftwiringfaults.

Boeing747-400

Boeing737-200's

Figure2"AirplanesprovidedforPEDEMIassessmentbyUnitedAirlines.

AlthoughUWBtestingwasnotapartoftheNASA/EWIstatementof work,allpartieswereinterestedinperformingapreliminarytest.Afterthecontractually-requiredtestingwascompleted,theEWI/UnitedAirlines/NASAteamworkedtogetherto seeif anUWBtransmittercouldaffectoperationalaircraftradiosystems.Unitedairlinesprovidedengineeringandmechanicsupport,aswellasfueledandoperationalairplanes.EWIprovidedengineeringsupportandNASAprovidedengineeringsupportaswellasUWBsourcesandinstrumentation.

4. 2 UWB Laboratory Signal Sources

As part of the FAA/NASA Interagency Agreement, four UWB sources were purchased in November,2001, for the purpose of studying UWB signal characteristics using standard EMC instrumentation, and to

assess future instrumentation requirements needed to quantify UWB signals as EMI threats. The UWBsources are shown in Figure 3. Each UWB source has an internal 9V battery, and has a jack for external

power using a 9VDC source. There is also a jack for switching on/off UWB pulses by using an externalTTL clock signal. If an external TTL clock signal is not available, the unit has an internal 10MHz TTL

clock that can be used by placing the CLOCK EXT/INT switch in the INT position.

When operated, the UWB sources emit extremely short duration electrical pulses from their output

jack. The manufacturer provided data specifications for the electrical pulses as follows:

Output Voltage (peak to peak)=Risetime=

Fall Time=

Pulse Width (RMS)=

6.7 + 0.3 V.

259 + 5 picoseconds

116 + 7 picoseconds

239 + 10 picoseconds

Because the UWB source output pulses are of such short duration, they contain frequency components

that span several GHz. Figure 4 shows a close-up spectrum analyzer display of the UWB source output in

the frequency domain, measured at NASA LaRC.

(a)

(b)

Figure 3: a) Laboratory UWB Signal Source. b) Set of 4 UWB Signal sources being tested for RF spectrum

characteristics. Function Generator used for external clocking is also shown.

Figure 4: a) Spectrum Analyzer display of UWB source output, from 1 MHz to 3 GHz. b) Manufacturer datashowing typical UWB pulse shape in the time domain.

4.3 UWB Testing on 3/22/2002, B737-200

All objectives under NASA/EWI contract L-16099 were complete by 3/21/2002, allowing several

hours for UWB EMI assessment with a fully operational aircraft. The UWB signal source was operated

using its internal 9V battery and 10MHz internal clock, and connected to an antenna tuned for the

frequency band of the aircraft radio system being evaluated. A list of test equipment is provided in Table

1. Spectrum Analyzer and antennas were verified to be within calibration schedule limits. UWB EMI

assessment was performed on the VHF Omni-Ranging (VOR), instrument landing system (ILS)

Localizer, ILS Glideslope, traffic collision avoidance system (TCAS), air traffic control radio beacon

system (ATC), and VHF Comm. aircraft radio systems as described herein.

Item Description Manufacturer Model# and Serial/ID #Airplane

UWB Signal Source

Spectrum Analyzer3 FtCable

Antenna, Dual Ridge Horn "DRH" (1-18GHz)

Antenna, Reference Dipole Set (28-1000MHz)Hand Held VHF Radio (aircraft frequency band)

Digital Video CameraAircraft Radio Recievers:

VHF Comm

VOR/ILS (Localizer and Glideslope)ATC

TCAS

Aircraft Radio Antennas:VHF Comm

VOR/ILS Localizer

ILS GlideslopeATC

TCAS (Upper)

Boeing

AgilentPasternack

A H SystemsETS

ICOM

Sony

CollinsCollins

CollinsCollins

Sensor SystemsDorne&Margolin

Sensor Systems

Sensor SystemsCollins

737-200, UAL Nose #1989

Boeing SN 21751TFP-1000, S/N 101

E4407B, NIMS# 16368133 ft. Low Loss

SAS-200/571, SN 164

3121C, NIMS# 2098522

DCR-TRV900, NIMS# 1613199

622-5218-005622-3257-008

622-7878-201622-8971-022

$65-8262-2DMN23-1/C

522-0700-023DMNI50-2-1

622-8973-001

Table 1: Equipment List for 3/22/2002 UWB EMI Testing

4.3.1 VHF Voice Communications

Test Procedure

A conversation was initiated and maintained between the aircraft VHF radio and handheld VHF radio.

The handheld VHF radio was operated from an automobile located about 30 ft away from the nose of the

aircraft, at both 118.02 MHz and 119.90 MHz. The UWB signal source was internally clocked (10MHz),

battery powered, and connected to the ETS 3121C dipole antenna (60-140MHz balun, with element

length set to 54.0cm), which was placed 1 meter away from the aircraft VHF-1 upper antenna (vertical

polarization). Using the test-setup in Figure 5, the UWB signal amplitude was measured to be -23 dBm

at 119.9 MHz, and less than -80dBm at 118.0 MHz. See Figure 6.

Figure 5:

Signal Source Spectrum IAnalyzer

Test arrangement for measuring UWB source output level.

E

0-10-20-30-40-50-60-70-80-90

MHz

Figure 6: UWB signal source output in the aircraft VHF communications frequency band, using 10MHz internalclock. Measured using spectrum analyzer peak detector, with 300kHz resolution bandwidth.

Observations

No discernable effect in audio quality was observed during the conversation.

4. 3. 2 ILS Localizer

Test Procedure

The local ILS Localizer beacon could not be acquired by the aircraft at the test location. The UWBsignal source was internally clocked (10MHz), battery powered, and connected to the ETS 3121C dipole

antenna (60-140MHz balun, with element length set to 64.6cm), which was placed 1 meter away from theaircraft VOR/Localizer tail antenna (horizontal polarization).

Observations

Cockpit instruments did not display any ILS Localizer information. No UWB effects were observed.

4. 3. 3 VORTest Procedure

The local VOR beacon was acquired by the aircraft at the test location. The UWB signal source wasinternally clocked (10MHz), battery powered, and connected to the ETS 3121C dipole antenna (60-

140MHz balun, with element length set to 64.6cm), which was placed 1 meter away from the aircraftVOR/Localizer tail antenna (horizontal polarization).

Observations

Cockpit instruments displayed appropriate navigation information for local beacon. No UWB effectswere observed.

4. 3. 4 ILS GlideslopeTest Procedure

The local ILS Glideslope beacon was marginally acquired by the aircraft at the test location. The

UWB signal source was internally clocked (10MHz), battery powered, and connected to the ETS 3121Cdipole antenna (140-400MHz balun, with element length set to 21.2cm), which was placed 1 meter away

from the aircraft Glideslope nose antenna (horizontal polarization).Observations

Cockpit instruments displayed appropriate navigation information for local beacon. No UWB effectswere observed.

4. 3. 5 A TC and TCAS

Test Procedure

The local ATC interrogator and TCAS transponders on aircraft in the local airspace were acquired by

the test aircraft. The UWB signal source was internally clocked (10MHz), battery powered, and

connected to the AH Systems dual ridge horn (DRH) antenna. Because interference was observed with

the horn antenna placed 1 meter away from the aircraft TCAS upper antenna, the test procedure was

expanded to include locations inside the passenger cabin with the aircraft doors closed.

Observations

The "ATC Fail" indicator lamp on the cockpit display panel illuminated, and airplane targets

disappeared from the TCAS display when the UWB signal source was turned ON. Video was recorded of

the EMI situation. This failure was observed with the UWB source transmitting from the followinglocations:

• Outside the aircraft, -1.5m from the aircraft upper TCAS antenna, port side. (DRH Pol. = Vert.)

• At all first class window locations (windows #1 to 6), port side. (DRH Pol. = Vert.) All aircraftdoors closed.

• At the 3rd window location in Coach class (window #9), port side. (DRH Pol. = Vert.) All aircraftdoors closed.

To quantify the level of local TCAS signals relative to UWB signals required to upset aircraft TCAS

operation, the instrumentation setup described in Figure 7 was used to acquire data shown in Figure 8. To

measure the output power directly from the UWB source, the test setup shown in Figure 5 was used. In

Figure 8, the black diamonds show spectrum analyzer data, collected after about 20 seconds in "Max

Hold" mode, with the UWB source turned OFF. This data was intended to show the amplitude of

ambient TCAS signals (from other airplanes and ground interrogators), as seen from the TCAS antenna

mounted on the top of the airplane. However, the spectrum is dominated by signals centered about 1090

MHz, which were likely to be the test aircraft's own ATCRBS Mode S reply transmissions.

TransmitCable

DRH Antenna Aircraft Antenna (((_

._ ~1.5 m _ I I• eacon" ATC

Figure 7: Schematic of test setup used to measure relative amplitudes of UWB and surrounding ATC/TCASsignals.

A few seconds after this spectrum analyzer trace was recorded, the UWB source was turned ON, andthe trace was recorded again to obtain the red triangles. (Note that during the 13 seconds before the

second trace was recorded, several more ambient signals were observed by the spectrum analyzer. Thesecan be readily identified as they follow the envelope of the other ambient signals, and should bedisregarded.) The green diamonds show the signal amplitudes directly out of the UWB source, as

measured using the Figure 5 test setup. This chart reveals a -20dB free-space/antenna/cable loss for theUWB source, when transmitting -1.5 m away from the TCAS upper antenna, versus being connected

directly into the spectrum analyzer. To accurately compare ambient TCAS and ATCRBS interrogatorsignals with the UWB source-transmitted signal at the TCAS receiver, it will be necessary to deactivate

the aircraft ATCRBS transponder in subsequent tests.

0

-10

-20

-30

_D

-40©

-50

-60

-701020

1989 TCAS UPR UWB Compare.pgw

1030 1040 1050 1060 1070 1080 1090 1100

Frequency (MHz)

Figure 8: Spectrum analyzer data showing ambient TCAS/ATC signals with UWB source signals. Measured usingspectrum analyzer peak detector, with 1 MHz resolution bandwidth.

This test conclusively demonstrated serious air traffic control system failures due to a battery-operatedUWB transmitter being operated on-board the aircraft. The output power directly from the source was

measured to be -30dBm (as shown in Figure 8). Adding a DRH antenna gain of 10 dB, the UWB sourcetransmitted an equivalent isotropic radiated power (EIRP) of-20dBm. Additional ATC/TCAS testingwas performed on 4/12/2002 and 5/8/2002, and is reported in Sections 4.4 and 4.5.

4.4 UWB Testing on 4/12/2002, B747-400

All objectives under NASA/EWI contract L-16099 were complete by noon, 4/12/2002, allowing about

two hours for UWB EMI assessment with a fully operational aircraft. The test team was prepared with

additional test capabilities compared to the previous visit. An external UWB source power supply and

HP 8116A Pulse Function Generator were provided by NASA to externally clock the UWB signal source,

and a portable VOR/ILS Ramp Test Set (TIC Tester) was provided by United Airlines to allow

transmission of ILS reference signals. A list of test equipment is provided in Table 2. The HP 8116A

Pulse Function Generator was set to output 1 microsecond pulses at the desired pulse repetition

frequency, and allowed external modulation of the UWB clock pulse by connecting a modulating signal

to its "Control-Input" jack. When selecting the "FM" modulation mode, the HP 8116A essentially

provided a dithered mode of pulse spacing to the UWB source clock input (by deviating the pulse

repetition frequency of the output clock pulses). When selecting the "AM" modulation mode, the HP

8116A essentially provided an On-Off-Keying mode of pulse control to the UWB source clock input

(depending upon whether the audio voltage output exceeded the TTL "1" level at the time of pulse

generation). A MicroCassette player audio signal was connected to the HP 8116A control-input jack,

while playing back a 30-minute segment of voice audio (recorded from the Weather Channel). The

Spectrum Analyzer, pulse function generator, TIC Tester and antennas were verified to be within

calibration schedule limits. UWB EMI assessment was performed on the ILS Localizer, ILS Glideslope,

traffic collision avoidance system (TCAS), air traffic control radio beacon system (ATC), GPS,

SATCOM aircraft radio systems as described herein.

Item Description Manufacturer Model# and Serial/ID #Airplane Boeing 747-400, UAL Nose #8188

Boeing SN 26877

UWB Signal Source TFP-1000, S/N 101

Spectrum Analyzer Hewlet Packard 8561E, NIMS# 1257651Pulse Function Generator Hewlet Packard 8116A, NIMS# 037346

TIC T30DVOR/ILS Ramp Test Set Cat. III150 Ft Cable RG214 150'#1

3 Ft Cable Pasternack 3 ft. Low Loss

A H SystemsETS

Antenna, Dual Ridge Horn "DRH" (1-18GHz)Antenna, Reference Dipole Set (28-1000MHz)

SAS-200/571, SN 164

3121C, NIMS# 2098522

Antenna, Biconical (30-1000MHz) Schwarzbeck UBAA9114/BBVU9135 SN 124

Digital Video Camera SonyGE

Collins

Collins

Collins

HoneywellCollins

Ball Aerospace

Sensor Systems

Sensor SystemsDorne&MargolinCollinsAdams-Russel

Ball Aerospace

MicroCassette Recorder

Aircraft Radio Recievers:VOR/ILS

ATCTCAS

GPS Sending UnitSATCOM Data Unit

SATCOM LNA/DiplexerAircraft Radio Antennas:

ILS Localizer

ILS GlideslopeATCTCAS

GPSSATCOM

DCR-TRV900, NIMS# 16131993-5376A

822-0282-120

822-0336-001

622-8971-022HG2021GC02

622-8848-001511610-500

$65-147-7$41422DM1601354-001

622-8973-001ANPClll-2

511611-500

Table 2: Equipment List for 4/12/2002 UWB EMI Testing

10

4. 4.1 ILS Localizer

Test Procedure

The VOR/ILS Ramp Test Set was placed about 20 ft (6 meters) from the nose of the airplane, and the

aircraft localizer radio receiver was captured with the 118.10 MHz test set reference signal. The UWB

signal source was externally powered and externally clocked with the HP 8116A Pulse Function

Generator at 9.99MHz, to place a UWB frequency component at 118.10 MHz, coinciding with the ILS

localizer test set channel. The UWB source was connected to a 150 ft length of RG214 coaxial cable,

allowing the ETS 3121C dipole antenna (60-140MHz balun, with element length set to 64.6cm) to be

placed about 20ft (6 meters) from the aircraft ILS localizer nose antenna (horizontal polarization), next to

the VOR/ILS Ramp Test Set. Pictures of the aircraft ILS Localizer antennas and the VOR/ILS Ramp

Test Set are shown in Figure 9. Measured output data from the UWB source, when using both FM

(dithered) and AM (on-off keying) modulation techniques are plotted in Figure 10.

Figure 9: a) UWB source, external clocking instrumentation and spectrum analyzer, b) Nose view of B-747airplane, with radome open. c) VO1VILS Ramp Test Set ("TIC" Tester).

Observations

Radiated signals from the UWB transmitter caused uncommanded motion and blanking of the Course

Deviation Indicator bar on the aircraft Horizontal Situation Display. Failures occurred only when

applying FM to the UWB source clock input (dithered UWB), but not with AM (on-off keying) or no

modulation. Because of time limitations, no attempt was made to transmit from the UWB source inside

the aircraft, or to determine the minimum UWB transmit level at which the interference would occur.

Video was recorded of the cockpit display anomalies due to UWB EMI.

This test conclusively demonstrated serious ILS Localizer navigation failures due to a UWB

transmitter being operated near the aircraft. The output power from the source was measured to be

-20dBm, as shown in Figure 10. Adding a dipole antenna gain of 3 dB and subtracting the cable loss of

4dB, the UWB source transmitted an equivalent isotropic radiated power (EIRP) of-21 dBm. There was

no attempt to determine whether -21 dBm was the lowest EIRP at witch the failure would occur.

Additional ILS Localizer testing was performed on 5/8/2002, and is reported in Section 4.5.

11

-10

-20-30

-40

i -50-60

-70

-8o-90

O -100

118.10 MHz

-_L 2 _-__--_--:_ _-_-:_ _-: L-_: _-__-_:_-i NO Modulation 2 _-__-_:_--@_ _-__:: _- ---_,_ .................

................ ................. _................. ........... _ ................. .................. _................. I

F- ......................_..............77:7 I:T 7:7:::::7:7Ti:: T77: 71:,: ::7:77:i: 7:7::7T 17 7 7:i:7100

-10

105 110 115 120

-20 i-i ii--i--ii i-i i i ii i i iii i iii i i iii ON-OFF KeyinR ....... ' .............. :.............._2_ "Amplitude Modulation (AM)" of UWB clock ...........

-30 ....: _40

-50

o -60

-70-80=

O -90-]00 - I

100 105 110 115 120

-10 _= .................................... I.....................................-,, _-_ _ Dithering .................... I................... _--r_-_-_._--_- .....-20 ...........................................................................................................................................................m m_Jff- "F,q .... yModulation0SM)" I_mu,mu;

-40 _::::i:::1:!:221:i::22: : :2:2....".._.L.w.::!"..:_..........................t.........1:2 :::o -:o

-70

O -90

-100

100 105 110 115 120

Frequency (MHz)

Figure 10: Spectrum analyzer data, comparing UWB frequency spectra in the VOR/LOC band, when applyingdifferent modulations to the UWB source clock. The ON-OFF keying (AM) and Dithered (FM) spectra are actually

very dynamic, whereas these plots are merely a snapshot in time. Data was measured using the spectrum analyzerpeak detector, with a 300 kHz resolution bandwidth.

4. 4. 2 ILS Glideslope

Test Procedure

The VOWILS Ramp Test Set was placed about 20 ft (6 meters) from the nose of the airplane, and the

aircraft ILS glideslope radio receiver was captured with the 334.70 MHz test set reference signal. The

UWB signal source was externally powered and externally clocked with the HP 8116A Pulse Function

Generator at 9.72MHz, to place a peak UWB frequency component at 334.6 MHz, coinciding closely to

the ILS glideslope test set channel. The UWB source was connected to a 150 ft length of RG214 coaxial

cable, allowing the Schwarzbeck biconical antenna (very efficient in Glideslope frequency band) to be

placed about 20ft (6 meters) from the aircraft ILS glideslope nose antenna (horizontal polarization).

Pictures of the aircraft ILS glideslope antennas and the VOR/ILS Ramp Test Set are shown in Figure 9.

Observations

Radiated signals from the UWB transmitter appeared to sometimes cause intermittent motion and

blanking of the glideslope deviation indicator on the aircraft Horizontal Situation Display. However, it

was difficult to correlate the display events with UWB transmission. There was no difference when

applying FM (dithered UWB), AM (on-off keying) or no modulation to the UWB source clock input. No

attempt was made to transmit from the UWB source inside the aircraft, or to move the UWB transmitter

closer to the aircraft ILS glideslope antenna. Additional ILS glideslope testing was performed on

5/8/2002, and is reported in Section 4.5.

12

4. 4. 3 A TC and TCAS

Test Procedure

The local ATC interrogator and TCAS transponders on aircraft in the local airspace were acquired by

the subject aircraft at the test location. Testing was performed with the UWB signal source either

internally clocked (10MHz) or externally clocked at various frequencies, powered either externally or by

battery, and connected to the AH Systems dual ridge horn (DRH) antenna. External clock frequencies

were selected to place UWB frequency components at 1030 MHz and 1090 MHz and to approximate

various pulse spacings and time-slot durations used by the ATC and TCAS receivers. It was planned to

first observe interference with the horn antenna placed 1 meter away from the aircraft TCAS upper

antenna, and to extend the survey to include locations inside the passenger cabin.

Observations

An "ATC Fail" message was observed on the cockpit display panel, and airplane targets disappeared

from the TCAS display when the UWB signal source transmitted out the pilot's escape hatch, about 1

meter away from the top TCAS antenna. The view from the pilot's escape hatch is shown in Figure 11.

The failure was reproduced when using different UWB clock frequencies when transmitting out the

pilot's escape hatch. However, with the UWB source transmitting from inside the cockpit or out the

passenger cabin window, no effect was observed to the aircraft ATC/TCAS systems. Table 3 shows the

various test configurations and observations. Video was recorded of the cockpit display anomalies due toUWB EMI.

GPS Antennas

Top TCAS

VHF comm

Antenna

Low Gain

Figure 11: View through the pilot's escape hatch on top of a Boeing 747-400 airplane.

ATC Antenna

Location

Cockpit Hatch

Cockpit Hatch

UWB Clock

Freq.20MHz

4MHz

UWB ClockModulation

None

None

Observed effect

ATC Fail, TCAS loss of targets.No effect.

Cockpit Hatch 8MHz None ATC Fail, TCAS loss of targets.20MHzWindow Upr. Starboard #1

Window Upr. Starboard #1

Window Upr. Starboard #1

Window Upr. Starboard #1

Window Upr. Starboard #1Pilot Seat

10.2MHz

8MHz

None

None, FM, AM

None, FM, AM

None, FM, AM

None, FM, AMNone, FM, AM

4MHz

500kHz

20MHz

No effect.

No effect.

No effect.

No effect.

No effect.

No effect.

Pilot Seat 20MHz None, FM, AM No effect.10MHz

(internal)Cockpit Hatch & OtherLocations

None ATC Fail, TCAS loss of targets, only when

transmitting outside hatch, nowhere else.Table 3: Test cases for ATC/TCAS on B747 aircraft

13

This test conclusively demonstrated serious air traffic control system failures due to a UWB

transmitter being operated outside the aircraft. The output power from the source was measured to be

-30dBm. Adding a DRH antenna gain of 10 dB, the UWB source transmitted an equivalent isotropic

radiated power (EIRP) of -20dBm. Additional ATC/TCAS testing was performed on 5/8/2002, and is

reported in Section 4.5.

4. 4. 4 GPS and Satcom

Test Procedure

Acquired GPS satellite navigation UTC & position and Satcom Link Status "OK" on the aircraft

system information display. Testing was performed with the UWB signal source either internally clocked

(10MHz) or externally clocked at various frequencies, powered either externally or by battery, and

connected to the AH Systems dual ridge horn (DRH) antenna. External clock frequencies were selected

to place UWB frequency components at 1575.42 MHz and to approximate the GPS C/A code clock rate.

It was planned to first observe interference with the horn antenna placed just outside the pilot's escape

hatch, about 3 meters away from the aircraft GPS upper antenna and about 2 meters away from the

Satcom low-gain antenna, and to extend the survey to include locations inside the passenger cabin. The

GPS antenna and the Satcom low-gain antennas can be seen as the small, flat, white patches and the black

blade farthest towards the airplane tail, respectively, in Figure 11.

Observations

No effect was observed with the GPS satellite navigation UTC and position and Satcom Link Status

"OK" indication on the aircraft system display UWB source. Table 4 shows the various test

configurations and observations. The GPS satellite navigation UTC and position and Satcom Link Status

indications do not provide much insight into possible signal interference. Given there were only a few

minutes available to perform the assessment due to time limitations, it is not surprising that nointerference effects were observed.

Location

Cockpit Hatch & Window

Upr. Starboard #16"

UWBClock

Freq.10MHz

(internal)

UWB ClockModulation

None

Observed effect

No effect.

Cockpit Hatch 16.3MHz None No effect.

Cockpit Hatch 1.02MHz None No effect.None, FM, AMCockpit Hatch 20MHz No effect.

Table 4: Test cases for GPS and Satcom on B747 aircraft. *Window Upr. Starboard #16 was the location of leastinterference path loss between the passenger cabin and GPS antenna.

14

4.5 UWB Testing on 5/8-9/2002, B737-200

From 5/8/2002 to 5/9/2002, approximately 6 hours was allocated for UWB EMI assessment with a

fully operational aircraft. The primary goal was to duplicate the ILS Localizer interference found on the

B747-400, and to better quantify the UWB interference thresholds found previously for the ILS, TCAS

and ATC aircraft systems. A list of test equipment is provided in Table 5. Again, an external power

supply and HP 8116A Pulse Function Generator were provided by NASA to externally clock the UWB

signal source, and a portable VOR/ILS Ramp Test Set (TIC Tester) was provided by United Airlines to

allow transmission of ILS reference signals. The HP 8116A Pulse Function Generator was set to output 1

microsecond pulses at the desired pulse repetition frequency, and allowed external modulation of the

UWB clock pulse by connecting a modulating signal to its "Control-Input" jack. When selecting the

"FM" modulation mode, the HP 8116A essentially provided a dithered mode of pulse spacing to the

UWB source clock input (by deviating the pulse repetition frequency of the output clock pulses). When

selecting the "AM" modulation mode, the HP 8116A essentially provided an On-Off-Keying mode of

pulse control to the UWB source clock input (depending upon whether the audio voltage output exceeded

the TTL "1" level at the time of pulse generation). A MicroCassette player audio signal was connected to

the HP 8116A control-input jack, while playing back a 30-minute segment of voice audio (recorded from

the Weather Channel). The Spectrum Analyzer, pulse function generator, TIC Tester and antennas were

verified to be within calibration schedule limits. UWB EMI assessment was performed on the ILS

Localizer, ILS Glideslope, traffic collision avoidance system (TCAS), and air traffic control radio beacon

system (ATC) aircraft radio systems as described herein.

Item Description Manufacturer Model# and Serial/ID #Airplane (ILS Localizer and Glideslope tests) Boeing 737-200, UAL Nose #1879

Boeing SN 21544

Airplane (ATC and TCAS tests) Boeing

UWB Signal Source

737-200, UAL Nose # 1994

Boeing SN 22384TFP-1000, S/N 101

Spectrum Analyzer Hewlet Packard 8561E, NIMS# 1257651Pulse Function Generator Hewlet Packard 8116A, NIMS# 037346

VOR/ILS Ramp Test Set Cat. III50 Ft Cable

TIC T30DRG214 50'#1

50 Ft Cable RG214 50'#5

3 Ft Cable Pasternack 3 ft. Low Loss

Antenna, Dual Ridge Horn "DRH" (1-18GHz)

Antenna, Reference Dipole Set (28-1000MHz)Antenna, Biconical (30-1000MHz)

A H SystemsETSSchwarzbeck

SonyGE

Collins

CollinsCollins

Dorne&MargolinSensor Systems

Sensor SystemsCollins

Digital Video CameraMicroCassette Recorder

Aircraft Radio Recievers:

VOR/ILS (Localizer and Glideslope)ATC

TCAS

Aircraft Radio Antennas:VOR/ILS Localizer

ILS GlideslopeATC

TCAS (Upper)

SAS-200/571, SN 164

3121C, NIMS# 2098522UBAA9114/BBVU9135 SN 124

DCR-TRV900, NIMS# 16131993-5376A

622-3257-008

622-7878-201622-8971-022

DMN23-1/C

522-0700-023DMNI50-2-1

622-8973-001

Table 5: Equipment List for 5/8-9/2002 UWB EMI Testing

15

4. 5.1 ILS LocalizerTest Procedure

The VOR/ILS Ramp Test Set was operated from the cockpit of the airplane (UAL Nose #1879), and

the ILS localizer radio receiver was captured with the 108.15 MHz test set reference signal. The UWBsignal source was externally powered and externally clocked with the HP 8116A Pulse FunctionGenerator at 9.97MHz, to place a UWB frequency component at 108.15 MHz, coinciding with the ILS

localizer test set channel. The UWB source was connected to two 50 fi lengths of RG214 coaxial cableconnected inline, allowing the ETS 3121C dipole antenna (60-140MHz balun, with element length set to

64.6cm) to be placed anywhere within the airplane passenger cabin. A picture of the aircraft ILSLocalizer antenna is shown in Figure 12.

Figure 12: a) Aft view of B-737 passenger cabin, b) Tail view of B-737 airplane. The two VOR/ILS Localizerantennas are parallel to one another, and are embedded horizontally within the top edge of the aircraft tail. Thecorner tip section has been removed in the photograph, to expose the two RF cable connections to the two antennas.

Observations

Two sets of testing were performed. On 5/8/2002, the goal was to repeat the UWB interferencesituation witnessed on the ILS Localizer during the 4/12/2002 testing. The VOR/ILS Ramp Test Set

output attenuation was adjusted such that -4.3 dBm maximum power was delivered to its antenna at108.15 MHz. The output power from the UWB source was measured to be -20dBm, using the spectrum

analyzer (as previously described in Section 4.3.5). Adding a dipole antenna gain of 3 dB and subtractingthe cable loss of 4dB (100fi, RG 214 @110 MHz), the UWB source transmitted an equivalent isotropic

radiated power (EIRP) of-21dBm. Table 6 shows the various test configurations and observed effects.Test dipole antenna polarization was horizontal in all cases. For test window locations, the dipole antenna

was centered in the window, as close to window as possible. In all cases, "LOC Fail" was characterizedby erratic motion and retraction of the Course Deviation bar on the HSI, and erratic motion and retraction

of the Localizer pointer and extension of the LOC Fail flag on the ADI.

16

Location UWB Clock Observed effectModulation

6m in front of aircraft nose FM LOC FailFM No effectDoor, Port #2 (aft)

Window, Port #33 (last one)Window, Port

Erratic Course Dev and Loc Pointer motionFM#32 FM#32#31 FM#30 FM#29 FM

#28 FM#27 FM#26 FM#25 FM#24 FM#23 FM#22 FM#21 FM#20 FM#19 FM#18 FM#17 FM#16 FM#15 FM#14 FM#13 FM#12 FM#11 FM#10 FM#9 FM#8 FM#7 FM#6 FM#5 FM#4 FM#3 FM#2 FM#1 FM

LOC Fail

Window, Port None No effectWindow, Port LOC FailWindow, Port LOC FailWindow, Port LOC FailWindow, Port LOC FailWindow, Port LOC FailWindow, Port No effectWindow, Port No effectWindow, Port No effectWindow, Port LOC FailWindow, Port LOC FailWindow, Port LOC FailWindow, Port LOC FailWindow, Port LOC FailWindow, Port LOC FailWindow, Port LOC FailWindow, Port Erratic Course Dev and Loc Pointer motionWindow, Port No effectWindow, Port No effectWindow, Port No effectWindow, Port No effectWindow, Port No effectWindow, Port No effectWindow, Port No effectWindow, Port Some LOC Pointer deflectionWindow, Port No effectWindow, Port No effectWindow, Port No effectWindow, Port No effectWindow, Port No effectWindow, Port No effectWindow, Port No effectWindow, FM No effect

Table 6: Test cases for ILS Localizer on a B737-200 aircraft, with UWB source transmitting at -21dBm EIRP

On 5/9/2002, the goal was to quantify the UWB interference thresholds found previously for the ILS

Localizer aircraft system. To approximate the FCC UWB limits for Outdoor Handheld Systems

(published at _ov.,'B_._reaus/[__ Tech_ol_;_.,'News Releases/2OO2/r_ret0203_, as -41 dBm

below 960MHz), a 20 dB attenuator was placed inline at the output of the UWB source. Adding a dipole

antenna gain of 3 dB and subtracting the cable loss of 4dB (100ft, RG 215 @110 MHz), the UWB source

transmitted an equivalent isotropic radiated power (EIRP) of -41dBm. The VOR/ILS Ramp Test Set

output attenuation was adjusted such that -34.5dBm was delivered to its antenna at 108.15 MHz. This

was a minimum output power at which the aircraft ILS localizer system provided stable lock for the HSI

and ADI Localizer indications. Table 7 shows the various test configurations and observed effects.

17

Location UWBClock ObservedeffectModulation

Window,Port#30 FM LOCFailWindow,Port#29 FM LOCFailWindow,Port#28 FM LOCFailWindow,Port#27 FM NoeffectWindow,Port#26 FM NoeffectWindow,Port#25 FM NoeffectWindow,Port#24 FM NoeffectWindow,Port#23 FM NoeffectWindow,Port#22 FM NoeffectTable7: TestcasesforILSLocalizeronaB737-200aircraft,withUWB source transmitting at MldBm EIRP

This test conclusively demonstrated serious ILS Localizer navigation failures due to a UWB

transmitter being operated inside the aircraft, transmitting near levels the FCC has approved for marketing

and operation of inexpensive handheld UWB devices. A video was recorded of the cockpit displayanomalies due to UWB EMI.

4. 5. 2 ILS Glideslope

Test Procedure

The VOR/ILS Ramp Test Set was operated from the cockpit of the airplane (UAL Nose #1879), and

the ILS glideslope radio receiver was captured with the 334.55 MHz test set reference signal. The UWB

signal source was externally powered and externally clocked with the HP 8116A Pulse Function

Generator at 9.98MHz, to place a UWB frequency component at 334.55 MHz, coinciding with the ILS

glideslope test set channel. The VOR/ILS Ramp Test Set output attenuation was adjusted such that -17.2

dBm was delivered to its antenna at 334.55 MHz. The UWB source was connected to a 50 ft length of

RG214 coaxial cable, allowing the Schwarzbeck biconical antenna (very efficient in Glideslope frequency

band) to be placed near the ILS glideslope nose antenna (horizontal polarization). The output power from

the UWB source was measured to be -21 dBm, using the spectrum analyzer (as previously described).

Adding a biconical antenna gain of 3 dB and subtracting the cable loss of 2.4 dB (50ft, RG 214 @335

MHz), the UWB source transmitted an equivalent isotropic radiated power (EIRP) of -20.4 dBm. A

picture of the aircraft ILS glideslope antenna is shown in Figure 13.

Observations

Radiated signals from the UWB transmitter caused erratic motion and retraction of the GS bar and

GS pointer and extension of the GS Fail flag on the HSI and ADI, respectively. There was no difference

when applying FM (dithered UWB), AM (on-off keying) or no modulation to the UWB source clock

input. These failures were only observed when the UWB source was transmitting from outside the

aircraft (in front of the nose), but not when transmitting from within the passenger cabin. A video wasrecorded of the EMI situation.

18

ILS Glideslope Antenna

Figure 13: Nose view ofB-737 airplane, showing ILS Glideslope antenna.

4.5.3 ATC and TCAS

Test Procedure

The local ATC interrogator and TCAS transponders on aircraft in the local airspace were acquired by

the test aircraft (UAL Nose # 1994). The UWB signal source was internally clocked (10MHz), battery

powered, and connected to the AH Systems dual ridge horn (DRH) antenna. This test was similar to that

performed on 3/22/02, but was supplemented with measurements on the starboard side of the airplane

passenger cabin. (The B737-200 aircraft TCAS antenna is installed somewhat toward the port side of the

aircraft centerline, thus providing better coupling to the port side passenger cabin windows when

compared to the starboard side.) For an additional test, to approximate the threat of a UWB device

transmitting at the FCC 15.209 limits, a 20dB attenuator was placed inline at the output of the UWB

source.

Observations

The "ATC Fail" indicator lamp on the cockpit display panel illuminated, and airplane targets

disappeared from the TCAS display when the UWB signal source was turned ON, transmitting from the

first 3 port-side windows, inside the passenger cabin. The interference effects dissipated when adding the

20 dB attenuator inline, on the output of the UWB source. Interference effects were observed on the

starboard side only when the UWB source was transmitting out the starboard door, about 1.5m from the

aircraft TCAS antenna. Failure conditions are summarized in Table 8. Video was recorded of the cockpit

display anomalies due to UWB EMI.

19

Location Added Observed effectAttenuation

Door, Starboard #1 (front) none ATC Fail, Loss of TCAS targets.

Window, Starboard #1 No effectnone

Window, Starboard #2 none No effect

Window, Starboard #3 none No effect

Window, Port #1

Window, Port #2

Window, Port #3

none

none

none20dBWindow, Port #1

ATC Fail, Loss of TCAS targets.

ATC Fail, Loss of TCAS targets.

ATC Fail, Loss of TCAS targets.No effect

Window, Port #2 20dB No effect

Window, Port #3 20dB No effectTable 8: Test cases for ATC/TCAS on a B737-200 aircraft.

4. 6 Findings Summary

In summary, NASA, United Airlines and EWI have collaboratively revealed that UWB device

emissions can interfere with essential flight navigation radios. This work was performed as a voluntary

supplement to general PED EMI research on a non-interference basis. Table 9 provides an outline of the

findings.

Date of RF Aircraf Signal Signal UWB EMI Source UWB Failure DescriptionTest system t Type source Source Configuration EIRP

Config. Level Level[dBm] [dBm]

3/22/02 ATC & B737 Local Beacon ? Internal 10MHz

TCAS & Aircraft Clock, Xmit fromPort Side door #1,

windows 1-6, 9

4/12/02 ATC & B747 Local Beacon ? Internal 10MHz

TCAS & Aircraft Clock, Xmit fromPilot Escape Hatch

-20 ATC FAIL ON. Loss

of TCAS targets

-20 ATC FAIL ON. Loss

of TCAS targets

4/12/02 LOC B747 TIC, ? External Clock, FM, -21Monopole, Xmit from Aircraft118.10 MHz, NoseAircraft Nose

5/8/02 GS B737 TIC, -17.2 External Clock, -20.4Monopole, Xmit from Aircraft334.55 MHz, NoseCockpit

5/8/02 LOC B737 TIC, -34.5 External Clock, FM, -41Monopole, Xmit from Aft.108.15 MHz, Passenger CabinCockpit

5/9/02 ATC & B737 Local Beacon ? Internal/External -20

TCAS & Aircraft Clock, Xmit fromDoor #1 both sides

windows 1,2,3Stbd. side

Erratic motion and

blanking of CDI onHSI Display

Erratic GS Bar &

Pointer, GS Fail Flagon ADI, HSI

Erratic motion andretraction of CDI on

HSI Display

ATC FAIL ON. Loss

of TCAS targets

Table 9: Summary of cockpit display anomalies caused by UWB EMI to aircraft navigation radios.

20

5 Conclusions

It has been conclusively demonstrated that a handheld, low-power UWB transmitter can interfere with

aircraft TCAS, ATC, ILS localizer and ILS glideslope radios. Failure was demonstrated to occur on a

B737 aircraft ILS localizer system with UWB EIRP levels as low as -41dBm. Measurements wereperformed on two types of Boeing passenger jets. It is likely that EMI will occur at lower UWB EIRPlevels on smaller regional airplanes, because of better electromagnetic coupling to aircraft antennas from

their passenger cabins. Testing was very limited, and not likely to reveal the full degree of aircraft systemsusceptibilities. Several important aircraft systems were not considered at all, including radar altimeters,microwave landing systems, and DME. If the FCC 15.519 limits are modified, or particular devices

exceed the limits, it is more likely that UWB EMI to aircraft ATC/TCAS and other systems will occur.

Testing demonstrated that modulation of the UWB signal greatly influenced the susceptibilitythreshold of the ILS localizer radio. It is likely that the modulation technique used in this test was not

worst-case. A more detailed test, with careful attention to modulation parameters would likely inducefailures at lower UWB EIRP levels. The VOR and VklF communication systems were not tested for

increased susceptibility to modulated UWB, nor were they tested for susceptibility when receivingcommunication signals close to their receiver sensitivity limits. It is possible that these systems may have

susceptibilities that are as yet undiscovered.

The focus of the NASA/United/EWI testing was directed only towards handheld UWB systems.

Other legitimate UWB applications, such as imaging systems, ground penetrating radars, surveillance

systems, vehicular radars, and various communications and measurement systems may also pose a threatto air traffic control and aircraft navigation and communication systems. More detailed analysis andtesting of UWB device impact upon flight-essential aircraft navigation and communication systems, and

air traffic control is strongly recommended, particularly before unlicensed devices are widely available.The additional FCC Order of July 12,2002 [7], permitting the continued operation of UWB GPRs and

wall imaging systems that do not comply with the FCC Final Rule, indicates that the FCC will likelycontinue to loosen UWB transmitter restrictions until harmful interference is proven to occur.

6 Recommendations for Additional Aircraft System UWB EMI Assessment

As yet, there is insufficient information to predict how widespread operation of UWB devices may

impact the safety of passenger air travel. The goal for subsequent analysis and testing should be toprovide data for establishing well-defined, enforceable regulations that avoid unnecessary restrictions of

UWB applications, while guaranteeing that UWB products do not jeopardize passenger safety andsecurity when traveling on board airplanes. Such a task is larger in scope than any government agency,

product manufacturer, airline or university can effectively complete alone.

A three-element approach is recommended, including °analysis and laboratory testing, efield-testing

on operational aircraft, and °development of regulatory policies based upon authoritative technical merit.

The radio signal structure for all aircraft navigation and communication systems should be studied todetermine interfering signal modulation characteristics and levels that are required to impact aircraft radio

performance. Analysis of UWB device modulation approaches must be performed to identify the mostthreatening types, and quantify amplitudes required to threaten aircraft radio system performance. Actual

commercial UWB products should be tested for emissions in aviation frequency bands, with particularcare to use resolution bandwidths narrow enough to resolve aircraft frequency channels. Closed-loop

navigation system testing, incorporating actual flight hardware and trained pilots, should be performed to

21

specifically describe symptoms and anomalies that may be caused by interfering UWB signals, so that

flight crews can readily determine whether they are experiencing an EMI situation.

Aircraft field-testing is necessary for pre-screening to reveal likely problem areas, and for validation of

analytical studies and laboratory test predictions. Once the UWB signal levels required to impact aircraft

radio performance are known, the expected IPL between particular passenger-cabin locations and

particular aircraft radios (via their antennas) can be evaluated to determine minimum UWB handheld

device emissions required for interference. These predictions should be validated during aircraft field-

testing. The tests documented in this report fall into the pre-screening category. Additional pre-screening

is recommended before completing analytical studies on several aircraft systems, particularly VHF

communications, VOR, and ILS Glideslope. Such prescreening should include minimizing desired signal

amplitude available to the aircraft antenna, to optimize the potential for UWB signal interference.

Prescreening should also include applying various modulations to the UWB source clock.

Results of all analysis and test should be made publicly available for peer review and verification.

Airlines, UWB device manufacturers, airborne radio manufacturers, universities and government (FAA,

FCC, NASA, NTIA) should interact and cooperate to generate sound technical data and perform

comprehensive analysis to develop regulatory policies with the safety and security of the public in mind.

References

[1] G. F. Ross, "Transmission and Reception System for Generating and Receiving Base-band Duration Pulse

Signals Without Distortion for Short Base-band Pulse Communication System", U. S. Patent 3,728,632, datedApril 17, 1973. (Avail. From _://www.maltis_ectral.com,'?rfistorvffitiv])

[2] R. J. Fontana, "Recent Applications of Ultra Wideband RADAR and Communications Systems", Ultra-Wideband, Short Pulse Electromagnetics, Klewer Academic/Plenum Publishers 2000. (Avail. From

_? ://www.m_fltispectral.com/historv.htm_ )

[3] T. E. McEwan, "Ultra-Wideband RADAR Motion Sensor", U. S. Patent 5,361,070, dated November 1, 1994(Avail. From _://www.multisJ2ectral.com/hist_-¢.hm-Jl)

[4] D. Stover, "RADAR on a Chip, 101 Uses In Your Life", Popular Science Magazine, March 1995, p. 107.

[5] Federal Register / Vol. 67, No. 95 / Thursday, 5/16/02, "Ultra-Wideband Transmission Systems", ET DocketNo. 98-153, 17 FCC Rcd. 7435 (2002)

[6] 47CFR Ch. 1, Part 15.209, "Radiated Emission Limits; General Requirements", US Code of Federal Regulations,Federal Register dated December 18, 2001.

[7] "Revision of Part 15 of the Commission's Rules Regarding Ultra-Wideband Transmission Systems", DA 02-

1658, ET Docket No. 98-153, (Order), Released July 12, 2002.

[8] RTCA/DO-199, "Potential Interference to Aircraft Electronic Equipment from Devices Carried Aboard",

September 16, 1988

[9] RTCA/DO-233, "Portable Electronic Devices Carried on Board Aircraft", August 20, 1996.

[10] J. J. Ely, T. X. Nguyen, S. V. Koppen, M. T. Salud, "Electromagnetic Interference Assessment of CDMA and

GSM Wireless Phones to Aircraft Navigation Radios", AIAA DASC Conf., Oct. 2002.

22

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October 2002 Technical Memorandum

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Ultrawideband Electromagnetic Interference to Aircraft RadiosResults' of Limited Functional Testing With United Airlines and Eagles 722-64-10-53Wings Incorporated, in Victorville, CaliJbrnia 722-64-10-54

6. AUTHOR(S)

Jay J. ElyTimothy W. ShaverGerald L. Fuller

7. PERFORMING ORGANIZATION NAME(S)AND ADDRESS(ES)

NASA Langley Research CenterHampton, VA 23681-2199

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space AdministrationWashington, DC 20546-0001

8. PERFORMING ORGANIZATIONREPORT NUMBER

L-18238

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

NASA/TM-2002-211949

11.SUPPLEMENTARY NOTES

12a. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified-Unlimited

Subject Category 32 Distribution: StandardAvailability: NASA CASI (301) 621-0390

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

On February 14, 2002, the FCC adopted a FIRST REPORT AND ORDER, released it on April 22, 2002, and onMay 16, 2002 published in the Federal Register a Final Rule, permitting marketing and operation of newproducts incorporating UWB technology. Wireless product developers are working to rapidly bring thisversatile, powerful and expectedly inexpensive technology into numerous consumer wireless devices. Paststudies addressing the potential for passenger-carried portable electronic devices (PEDs) to interfere with aircraftelectronic systems suggest that UWB transmitters may pose a significant threat to aircraft communication andnavigation radio receivers. NASA, United Airlines and Eagles Wings Incorporated have performed preliminarytesting that clearly shows the potential for handheld UWB transmitters to cause cockpit failure indications forthe air traffic control radio beacon system (ATCRBS), blanking of aircraft on the traffic alert and collisionavoidance system (TCAS) displays, and cause erratic motion and failure of instrument landing system (ILS)localizer and glideslope pointers on the pilot horizontal situation and attitude director displays. This reportprovides details of the preliminary testing and recommends fitrther assessment of aircraft systems forsusceptibility to UWB electromagnetic interference.

14. SUBJECT TERMS

Ultrawideband, UWB, EMI, Electromagnetic, Interference, FCC, Aircraft, Avionics

17. SECURITY CLASSIFICATION

OF REPORT

Unclassified

18. SECURITY CLASSIFICATION

OF THIS PAGE

Unclassified

19. SECURITY CLASSIFICATION

OF ABSTRACT

Unclassified

15. NUMBER OF PAGES

2716. PRICE CODE

20. LIMITATION

OF ABSTRACT

UL

NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89)Prescribed by ANSI Std. Z-39-18298-102